The present invention relates generally to braking devices of the type used in conjunction with an electric motor. More particularly, the invention relates to such a braking device including an improved torque adjusting mechanism.
Braking devices are often used in conjunction with electric motors to arrest shaft rotation when the motor is deactivated. Often, these braking devices are configured as electromagnetic release, spring set units. In such an arrangement, spring force is applied against an armature (or "clapper") plate that engages friction material attached to a friction disk. The friction disk rotates with the motor shaft, and is connected thereto using a splined hub and key assembly. When the power is turned off, the spring force pushes the armature plate into engagement with the friction disk. Because the armature plate is stationary in the rotational direction, a resisting torque or force is imposed on the friction disk to cause the motor shaft to stop.
The amount of spring force on the armature plate can determine the period of time required to stop the load being driven by the motor. To permit control of the rate of braking, braking devices of this type are often provided with torque adjusting mechanisms. Many current designs use adjustable compression springs or a single compression spring in the inner diameter of the brake housing structure. To provide adjustment, the housing structure defines inner threads engaged by an adjusting nut. As the adjusting nut is threaded into and out of the housing, the spring is compressed or released through axial spacing change. The change in axial spacing will increase or decrease the spring force.
One disadvantage of this design is the axial spacing required to allow for the threading action of the adjusting nut. Because axial space is at a premium in many applications, a saving of even a small axial space would often be desirable.